A protection device is incorporated into circuits in various electrical circuits in order to protect electric or electronic apparatuses, electric or electronic components, and electric or electronic circuits where the circuits are incorporated in cases where there is a flow of a current which is larger than a rated current and/or a voltage which is higher than the rated voltage is applied.
Among such protection devices, a protection device, a so-called fusing register, is known which includes a thermal fuse and a resistor, the resistor generates heat due to current passing through the resistor when there are abnormalities, and the thermal fuse is activated due to this heat (Patent Document 1).
Use of a bimetal switch and a positive temperature coefficient (PTC) element connected in parallel is proposed as another protection device (Patent Document 2). In such a protection device, when there are conditions when overcurrent occurs, the bimetal portion of the bimetal switch reaches a high temperature and the contact point thereof separates and opens up, and the current is commutated to the PTC element. As a result, the PTC element effectively interrupts the current which flows in the PTC element due to the PTC element being tripped into a high temperature and high resistance state due to the overcurrent.